Benign papillary mesothelioma of the tunica vaginalis testis.

We report a case of benign mesothelioma of the tunica vaginalis testis in a 69-year-old man who presented with a 4-month history of scrotal swelling. A polypoid pedunculated nodule, 1.5 cm in diameter, was found near the head of the right epididymis. Histologically, the tumor exhibited features characteristic of a well-differentiated papillary mesothelioma. The mesothelial origin of this tumor was further supported by immunohistochemical analysis. The tumor cells exhibited nuclear p53 protein accumulation, despite the benign histologic findings and a 3-year uneventful follow-up after resection. A polymerase chain reaction analysis for simian virus 40 DNA was negative. The papillary configuration seen in this tumor is uncommon for this site, inasmuch as benign mesotheliomas of the tunica vaginalis testis usually exhibit an adenomatous pattern. One should be aware of this pattern, and benignity should be mentioned in the pathologic report to prevent overtreatment. In addition, positive p53 immunohistochemical staining should not be taken automatically as evidence for malignancy in this type of lesion.